Mercury switch



July 1, 1941- A. c. LINDsTRM 2,248,003

MERCURY SWITCH Filed Aug. 26, 1939 I of Patented July 1, 1941 UNITED STATE MERCURY SWITCH Alrk Civer Lindstrm, Stockholm, Sweden Application August 26, 1939, Serial No. 292,146 In Sweden August 30, 1938 (cl. 20o- 4152) I 9 Claims.

This invention relates to improvements in mercury switches and the like. 'I'he invention has reference particularly to mercury switchesv which consist of a closed rotatably mounted receptacle in which there are two mercury masses each in connection with an electrode. These mercury masses may be united with each other or separated from each other by tilting the receptacle from one end position to the other end position, whereby the electric circuit connectedV toi said electrodes is closed and interrupted, respectively.

One of the objects of the invention is to provide a mercury switch of very simple formV and construction, which is cheap in its manufacture and which has the advantage that the dimensions in an axial direction are reduced to a minimum.

Another feature of the invention relates to the method of fitting the electrodes which are of metal to the receptacle which is made of in sulating material. This new method renders it possible to make the spaces within the receptacle gas-tight so that no oxidation of the surface of the mercury can dccur.

According to the invention, the receptacle has an inner space for one mercury mass and an outer space for the other mercury mass, which outer space surrounds the inner space. Prefer ably, these spaces are annular, while the inner or centre space thereof may be cyilndrical. These spaces are so arranged relatively to each other and relative the axis of rotation of thek receptacle that the geometrical axes coincide with each other or are at least parallel with each other.

Other objects and uses of the invention will appear from a detailed description of the same which consists in the features of construction and combinations of parts hereinafter described and claimed.

In lthe drawing:

Fig. 1 is a transverse sectional View of one embodiment of the invention on the line I--I of Fig. 2.

Fig. 2 i-s a longitudinal sectional view vtaken on the line II-II of Fig. 1.

Fig. 3 is a section through a modified construction of a part belonging to the switch.

Fig. 4 is a vertical section through another embodiment of the switch, the section being taken alo-ng line IV-IV in Fig. 6.

Fig. 5 is a similar section along line V--V in Fig. 6.

Fig. 6 is a section along line VI--VI in Fig.`4.

Fig. 7 is a partial section through a detail of the switch. The cover shown in section in Fig. 6 has been left out in Figs. 4 and 5. v

The embodiment illustrated. in Figs. l and 2 concerns a mercury switch which comprises a base plate 2 on which are mounted two brackets 4 and 6 adapted to support the mercury receptacle in a rotatable manner and which at the same time serve as leads toI carry the current. A Vprotecting cover 8 xed to the base plate has an opening I0 through which extendsan arm or a handle I2 serving for actuating the switch. The tilting of the receptacle is limited by the ends of the opening, so that the receptacle may be moved from one end position shown by dotted lines at the left hand side to the other end position shown by dotted lines at the right hand side.

lThe receptacle proper of the switch consists ofga body vof insulating material having the form of a short cylinder which is hollow and externally is provided at the end surfaces with metal caps or lids I4 and I6 serving as elecf trodes. These metal caps and the central body are surrounded at the circumference and also at the end surfaces with a cover I8 which preferably consists of artificial resin, such as Bakelite, so that this cover may be applied by pouringv or pressing the raw material onto the central body. This cover I8 has a projection I2 by means of which the .switch may be tilted as desired. The metal caps I4 and I6 which preferably consist of iron or non-corrosive steel, inasmuch as these metals are more suitable for cooperation with mercury, have central projections 20, 22 which extend through the cover I3 andr serve as' journals for the receptacle. In order 'to improve the electrical contact the projections 20 and 22 are preferably provided with minor caps 24 and 26 of brass or similar materialof good conductivity which rest by means of ilanges against the brackets 4 and 6 and serve as journals in the holes 4' and 6 in said brackets.

The central body of insulating material consists preferably of refractory porcelain or other ceramic material. It has the form of two short coaxial tubes 28 and 30 which are united with each other at both ends by means of end walls 32 and 34. together with the end wall 32 are made in one piece before burning the porcelain body, while the end wall 34 is made by itself. During burn- Aving this wall 34 Will be sintered together with the three parts 28, 30 and 32, so that the joint The two tube-like parts 28 and 30y 1 disappears andthe body is constituted by a coherent mass. 3 joint on the other side of lthe body, so that the parts 28 and 30. are made integral with the end `Wall 34 before the burning, and it is further possible to divide the insulating body in any led together b-y using three or moreV parts.Y

imore than half of its volume. 4 lmass therefore fills the space-35, thechanneli) `andI the greater part of the space betweenthe;`

It is quite possible to place the For instance, it may be mount- According to another method the insulating body other manner.

i may be made by first forming and burning each part yand then join the parts together by glazing;

and 40 by means of which the two .spaces are in communication with the spaces between the 1 external surfaces of the ends walls andthe metal caps I4 and I3. The opening or channel 39A- eflfects communication Vbetween the external .an-

nulai` space 38 and the space adjacent the crap` 1 I6, while the opening or channel 4i) brings-:about communication-between the central space 36and the space adjacent the cap I4. VItis possibleto alter the arrangement of the channels as illus-l trated in Fig. 3, so .thatfthe external annular `space 38 has communication to the left and the central space r36 has Vcommunication to the right, The receptacle is lled with mercury up to' The one mercury end wall and the cap I4, and for this reason :it

always makes electric contacts with this'V cap I4.` QThe second mercury mass isfin the space 38, the ichannel 39 and the greater ypart ofthe space .bef ltween theV end wall and the cap I5, so that .the latter is 'always in -electric ,contact with the merlcury.V In the tubular part 30 ofthe insulating4 body .there is a radially directed channel 42 which `connects the central space 33 with the outer space 38 and by means .of which .the two mercuryr masses are .united with eachother when the ref `ceptacle is tiltedin a conuterclockwise.direction from the position shown with full .lines inFig..2T 4to the left hand position indicated by. dotted lines. In the opposite end position, that is to say thev lright hand position shown Withdotted lines,.the7

lextreme outer end of the channel 4.2 is-entirely `above the surface 48 of the vmercu-ryVso'that then the electric contact is interrupted. Preferably, lthe channel i2V is situated along. a line ,passing throughthe centre of the receptacle and forming 1an angle of approximatelyfi? with the horizontal.'

`when the .receptacleoccupies the position shown in Fig. 2 ,with full lines. This arrangement brings about theV advantage that theswitch withoutany `alteration whatever may be mounted on.a.hori..;y

line 44. Even in this case the `two mercury masses may be .united with each` other and Aseparated `from each other .by swingingthe handle t2 from one end position to the other .endpositiornVV The channels 39 and 40 are in communication The end with the lower part of the pertaining space in the insulating body, and in all positions of the switch during its use they are always under the free mercury surface and preferably also under the horizontal plane passing through the axis of the receptacle. Furthermore, preferably they are situated diametrically opposite to the channel 42, that is to say, along a line passing through the centre of the yreceptacle and'` forming an angle of apprziiinatelyi" with the horizontal when the switch occupies the intermediate position shown .with full lines in Fig. 2.

tmannerfas just mentioned in connection with the channel 42 to mount the switch as well vertically as'also horizontally, inasmuch as the channels ..3-91and01in--nofcase will be above the horizontal planepassing through the axis-of the receptacle.

thesame purposefserves also the form of the lre-L ceptacle which is symmetrical withv Arespect -to thea'xis Vofrctaticn and which, therefore, does not permit the transportation of mercury from one space to theother when actuating theV switch.

It is tobe. noted tha-t the spaces .betweenthe metalvcaps and the outer walls ofthe receptacler will never' be free of mercury but they are al Ways almost completelylled with mercury. If,

for instance, a superpressure should arise within the receptacle on account of interruptionrof the arc, there willA be nodangerthat an appreciable quantity of. mercury will be pressed into the said. 'spacesfa'nd thereafter be transported back in oppositedirection. Further, the arc or mercuryvapor arising thereby has no possibility to b e thrust against the vmetal caps .and to damage'the same or to'i'ncreas'e the contact resistance between the caps and the mercury.

The embodiment describedabove ,may` be sub-A jected to various changes-without. affecting the scope of the invention. One of such modified,

embodimentsris, shown in Figs. 4 to 7 and will nowl be described. n

This secondembodimentldiers from the one lfirst described by kthe fact that the receptacle which in theY first case .consists fof the vcentral body 28, 30, 32, ,34 andthe outer cover I8 ismade in one piece in the second embodiment. In making this kreceptacle Vthe method employed is similar als. when-making the rst embodiment,

that is vto say, one partl provided vwith recesses second projection .54 arranged approximately diametrically opposite'to the r-st one and -cooperating with a leaf spring .55 Yfor the purpose of limiting .the Vtilting movement of the receptacle. VVWiththisin view, this spring 55 hasY two shoulders-56and51, andthe spring is insertedv with its free endsintoslots 58 and 59 inthe base plate 2. In-a .manner similar to that shown Yin Fig. l the switch is surrounded by a protectingcover Y8 havingan opening i8. The main part 5l has a cylindrical inner space 60 and an annular outer space 6|. The inner or central space 60 is in communication by means of a radial channel 62 with the outer annular space 6I, and this latter is in communication by means of a radial channel 63 with the space at the right end surface of the part I.

'I'he lid 52 has an opening 64 through which mercury is lled into the receptacle when making the switch.

Both end surfaces of this central body are covered by metal caps 65 and 66. These caps have centrally an annular flange 61 so that an opening is provided through which mercury can be lled into the receptacle. Upon this mercury having been poured in, the said opening will be closed by means of a minor cap 10 having its end surface directed towards the receptacle. The closing of this opening will be carried out, for instance, in the following manner. On the outer circumferential surface of this cap will be applied some artificial resin, such as Bakelite, and a heated mandrel is inserted into the cap. By means of this mandrel the cap is inserted into the opening of the metal cap 65, the resin is thereby heated and in this way the small cap will be cemented to the flanges. As external protection and in order to obtain a better journal a third cap 1I for instance of brass, is fitted over the outside of the flanges and soldered thereto. The big caps 65 and 66 and also the minor cap 10 inserted into the openings of the former consist of iron or of non-corrosive steel, inasmuch as this material is most suitable for the cooperation with mercury.

The gas-tight xing of the metal caps to the central body will be carried out in the embodiment shown in Fig. 1 at the same time as the outer cover I8 of insulating material is applied thereto.

In the second embodiment the metal caps are fastened as shown in Fig. 7. The two end surfaces of the parts 5| and 52 have annular recesses 12 and 13. In correspondence to these recesses the metal caps 65 and 66 have an annular flange 14 and 15. At first a thermoplastic medium, such as Bakelite 11. is inserted into the recesses 12 and 13 and then the caps are mounted on the Bakelite by the application of heat. By this means the metal caps will be sealed to the central body. In order to x these metal caps also mechanically there is used a non-thermoplastic medium, such as porcelain cement 19 which is applied to the parts at the Vcorner formed between the circumference of the metal caps and the outer wall of the recesses.

In this second embodiment of the invention the channels 62 and 63 are arranged and situated in a manner similar to the first embodiment, that is to say, when the receptacle occupies an intermediate position the central line of these channels forms an angle of approximately 45 with the horizontal.

Several illustrative embodiments of the principles of the present invention have been described. Since various matters of combination, arrangement, structure and design may be modified without departing from the inventive features, it is not intended to limit the invention to such matters except so far as set forth in the appended claims.

What I claim is:

1. A tiltable mercury switch comprising, a receptacle mounted for rocking movement between two end positions, two electrodes on said receptacle, a mercury mass in contact with said electrodes in said receptacle, an insulating wall between each of the electrodes and a space in the receptacle, a further insulating wall extending between the rst-mentioned walls and dividing the space in the receptacle into an inner space and an outer space surrounding the inner space, said last-mentioned dividing wall having an aperture therein adapted on the rocking movement of the receptacle to be located above the mercury level in one end position of the switch and underneath .the mercury level in the other position of the switch, each of the first-mentioned walls havlng an aperture therein located underneath the mercury level in both positions of the switch and underneath a horizontal plane passing through the axis of rotation of the receptacle providing communication between one electrode and said inner space and between the other electrode and said outer space, and means holding the electrodes adjacent the ends of the receptacle.

2. A tiltable mercury switch as claimed in claim l, in which the inner and .the outer spaces are arranged in the same plane and at right angles to the axis of rotation of the receptacle.

3. A tiltable mercury switch as claimed in claim 1, in which the outer space is annular and the central space is cylindrical.

4. A tiltable mercury switch as claimed in claim 1, in which .the axes of the two spaces and the `axis of the receptacle are parallel with respect to each other.

5. A tiltable mercury switch as claimed in claim 1, in which the receptacle consists of a short hollow cylinder of insulating material, and the cylinder being provided at the end surface with metal caps serving vas the electrodes.

6. A tiltable mercury switch as yclaimed in claim 1, in which the receptacle consistsy of two coaxial tubes which are united at the end surfaces by means of end walls, one end wall having an opening which is in communication with the inner space and the other end wall has an opening which is in communication with the outer annular space.

'7. A tiltable mercury switch as claimed in claim 1, in which a handle integral with the receptacle is provided for rotating the receptacle.

8. A tiltable mercury switch as claimed in claim 1, in which the Aaperture providing communication between the two spaces is situated along a line which forms an angle of approximately 45 with the horizontal when the receptacle occupies a central position intermediate two end positions.

9. A tiltable mercury switch as claimed in claim 1, in which the apertures providing communication between ,the electrodes and the spaces in the receptacle are arranged along a line which forms an angle o-f approximately 45 with the horizontal when the receptacle occupies a central position intermediate two end positions.

ALRIK CIVER LINDSTRM. 

